This invention relates to a heat treating furnace of the type in which electric resistance heating elements are disposed within a work chamber to radiantly heat workpieces in the chamber. The work chamber is defined within a walled enclosure preferably having an outer wall and having radiation sheilding packs attached to the inner side of the outer wall.
To supply electrical power to the heating elements, elongated rigid conductors extend through the wall of the furnace. The inner end portion of each power feed through conductor is connected to one end of a heating element while the outer end portion of each conductor carries a terminal block adapted to be connected to a source of voltage for energizing the heating element. To dissipate heat from the power feed through conductor, cooling water is circulated through the conductor by means of inlet and outlet lines connected to the conductor.
Each power feed through conductor extends slidably through a hole in the furnace wall so that the conductor may be removed from the wall for repair or replacement. An insulating washer on the inner end portion of the conductor insulates the heating element electrically from the wall and provides thermal insulation around the hole through which the conductor extends. In some heat treating furnaces, the insulating washers become coated with metal which is vaporized during the heat treating process and, after some period of use, the washers tend to lose their insulating characteristics. Thus, the insulating washers must periodically be removed from the furnace and replaced with new washers.